1. Field of the Invention
This invention pertains to sorting machines used to sort fungible products, such as nuts and many other agricultural products, by passing the products along a channel having a viewing window and detecting products that are nonstandard in length from those that are within a range of standard sizes and rejecting those that are nonstandard.
2. Description of the Prior Art
A typical sorter of fungible products of the type just described is comprised of one or more channels that are gravity fed from a top loaded hopper, the products flowing in each of the channels in a fairly constant stream and sometime overlapping one another. The channel includes or leads to a viewing window through which the stream of flowing products are electro-optically observed by at least one photodetector to produce an output when there is a product in the window. Although only one photodetector is used in a very simple machine, it is common to employ multiple photodetectors, for example, three, for viewing the product flow from various viewing angles.
A product can be sorted on the basis of one or more criteria, including variance in overall color, variance in spot coloration, variance in length because of being either abnormally small or abnormally long. When a substandard product is viewed or sensed, a reject signal is produced that, following a suitable delay, results in the activation of a reject mechanism, which diverts the substandard product from the channel. The delay is necessary for the product to fall below the viewing window and be opposite the reject mechanism. The reject mechanism is typically a burst or jet of air that blows the substandard product out of the ordinary channel flow to cause the rejected product to drop into a reject bin.
Heretofore, it has been virtually impossible to sort by prior art machines products that are either abnormally long or abnormally short. That is, in many cases, broken pieces are desirably discriminated against and rejected as being substandard by being abnormally short. Abnormally long pieces are sometimes also considered substandard for a particular purpose and are rejected. For example, abnormally long almonds are not desirable for use in a candy bar.
When products are viewed singly by the prior art machines, they can be discriminated against since standard products would occupy an acceptable percentage of the overall viewing window or, alternatively, products that are substandard would occupy an abnormally small or large percentage of the overall viewing window. However, when the product flow is fast, as it desirably is with the newer machines, mistakes on this basis of discrimination do occur because of product overlap. A broken piece, that would be a substandard small product, may get by when included in the viewing window with at least part of another product. Perfectly acceptably sized products may be rejected when they appear together by being mistaken for an abnormally long product.
It is also important to time the reject mechanism consistently with the same part of the product, regardless of where a defect in a product is detected. For example, in a sorting machine operation actuating on spot detection, prior art machines timed the delay to activation of the reject mechanism based upon where the spot occurs. If the spot on a first product is located on the leading edge, the delay would be from the detection of the leading edge. If the spot on a second product is located on the trailing edge, the delay would be from the detection of the trailing edge. For a nominal setting of reject being based on a center spot location, one or both of the previous products might escape rejection.
It is therefore a feature of the present invention to provide improved timing of the reject mechanism in a sorting machine by applying digital timing techniques to always activate the reject mechanism from the detection of the trailing edge of the product to be rejected and to cause such rejection even when the trailing edge might be actually nondetectable because of product overlap in the viewing window.